A Hong Kong police officer was shot with an arrow on Sunday during the siege of a fortified central university campus, a new escalation after nearly six months of demonstrations in the fiercely divided city.

Hundreds of protesters with bricks, petrol bombs and makeshift barricades have held off riot police on roads surrounding the campus in the city’s Hung Hom district, just across Victoria Harbor from Hong Kong Island, for hours.

The authorities have responded with tear gas and water cannons in skirmishes that have stretched from early in the morning until well into the evening.

As violence has escalated in recent days, protesters have begun using bows and arrows against the police, and authorities said a media liaison officer was hit in the leg with an arrow during a skirmish Sunday afternoon.

in a fiercely worded statement, the police labeled the group holding the university “rioters,” a loaded term in Hong Kong’s protests which carries a heavy prison sentence if convicted.

The man who was shot with an arrow is conscious and has been sent to hospital for treatment, according to the police statement.

Hong Kong’s Polytechnic University is just one of a number of university campuses being used in the past week as a rallying point for Hong Kong’s protest movement.

But unlike other campuses such as the Chinese University of Hong Kong, the Polytechnic University sits in the center of the city, close to a number of major roads including a cross harbor tunnel.

In the past week, protesters have blocked these roads, severely disrupting the city’s public transport system.

Polytechnic University is also less than 164 feet (50 meters) from a Chinese People’s Liberation Army (PLA) base. So far there has been no sign that the country’s military will be used to crack down on protesters.

In a statement Sunday evening, the Hong Kong Professional Teachers’ Union and the university’s Staff Association said they were “very worried” about the safety of students and bystanders.

“We call on both sides to exercise restraint and avoid the use of deadly weapons. The current stalemate is caused by a series of government decision-making mistakes and should be resolved responsibly,” the statement said.

University campuses fortified

The protests in Hong Kong have now been raging for almost six months after they began in June over a controversial China extradition bill, which sparked huge marches across the city.

When the government suspended but didn’t withdraw the bill, the movement’s focus quickly expanded to focus on complaints of police brutality and wider calls for democracy.

The protests took a turn in early November after the protest-related death of a 22-year-old student, the first since the demonstrations began. Protesters began to fortify university campuses across the city, holding off police with weapons ranging from bows and arrows and petrol bombs.

On Saturday night police attempted to clear the roads around Polytechnic University but were forced to back down after protesters started fires on the street and threw petrol bombs.

“They showed total disregard for the safety of everyone at scene,” police said in a statement Sunday, confirming they tried to disperse the group using tear gas.

A 23-year-old protester and Polytechnic University alumni told CNN Sunday that they didn’t have a plan and were just waiting to see how the police would react. “If we don’t come out, no one will come out and protect our freedoms. Polytechnic University is my home,” he said.

Protesters on Sunday were using catapults to launch bricks and other hard objects at police lines from the university’s balconies. Their hold on the high ground made it difficult for police vehicles to advance under a hail of bricks and petrol bombs.

“Such attacks pose a grave threat to the safety of police officers, reporters and first aiders at the scene,” said police in a statement, accusing protesters of firing petrol bombs and metal balls at their lines.

On Sunday the government announced that all schools would be shut again on Monday as protests were expected to continue across the city.

Protests escalate

With the both the government and the protesters refusing to back down, there is no immediate end in sight to the Hong Kong demonstrations.

Showing his dissatisfaction with the situation, Chinese President Xi Jinping made rare public comments on the demonstrations Thursday.

He said that “radical” protesters had trampled the city’s rule of law and that “stopping the violence and restoring order” was Hong Kong’s most “urgent task.”

It came just hours before a 70-year-old man, who was struck by a brick during clashes between protesters and their opponents, died of his injuries. Police blamed protesters for throwing the item which killed him.

For the first time since the start of the demonstrations in June, China’s People’s Liberation Army hit the streets of Hong Kong on Saturday but only to clear up barricades and debris.

Even that incursion was enough to spur pro-democracy lawmakers in Hong Kong to push for an explanation from the city’s government.

Chinese soldiers’ efforts to clear road blocks outside their barracks in Kowloon Tong was “purely a voluntary community activity initiated by themselves,” the Hong Kong SAR government said in a statement to CNN.

Police launch water cannon and tear gas outside the Hong Kong Polytechnic University to disperse protesters in Hong Kong on Sunday.

A protester reacts from tear gas fired by police at the Hong Kong Polytechnic University in Hong Kong on Sunday.

Protesters use a catapult to fire objects at the police from inside the Hong Kong Polytechnic University in Hong Kong on Sunday.

A handout image from the Hong Kong Police shows an arrow in the calf of a Hong Kong police officer on Sunday, Nov. 17, 2019.